Suspension for pivotal track frames on terrain motor vehicles

ABSTRACT

A suspension for pivotal track frames on terrain motor vehicles of the kind where the tractor body is supported by one single pivotal track frame on opposite sides of the body. The frames are provided with track wheels or belts. The new suspension comprises a journal bushing fixed to each of the pivotal frames and defining the pivot axis therefore. In the bushing are positioned thick-walled, solid tube-shaped elastic linings made of rubber or the like and which encompass a coaxially extending support beam mounted to the tractor body. The outside and the inside surfaces of the elastic linings are not rotatably joined to the inside of the bushing and the outside of the beam, respectively, such that the pivotal movements of the track frames when the tractor is moving through terrain take place under flexible deformation of the linings, which linings thus operate as spring suspensions and shock absorbers.

United States Patent [191 Kasin et al.

[54] SUSPENSION FOR PIVOTAL TRACK FRAMES 0N TERRAIN MOTOR VEHICLES [75]Inventors: Hans Kasin; Odd Krane Thvedt,

both of Notodden, Norway [73] Assignee: Christianin Spigerverk, DivisionJOBU, Oslo, Norway [22] Filed: Apr. 5, 1971 [21] Appl. No.: 131,052

[52] U.S. Cl ..l80/9.54

[51] Int. Cl. ..B62d 55/10 [58] Field of Search ..l80/9.5, 9.54, 9.64,41;

[56] References Cited UNITED STATES PATENTS 1,429,474 9/1922Wickersham... .,...180/9.5

2,537,745 l/1951 Daniels ..305/27 2,434,693 l/1948 Graham "ISO/9.54

2,951,710 9/1960 Willetts ....280/l04.5 A

1,985,777 12/1934 Hamilton ..180/9.64 X

Primary Examiner-Richard J. Johnson Attorney-Wenderoth, Lind 8L Poznack[57] ABSTRACT A suspension for pivotal track frames on terrain motorvehicles of the kind where the tractor body is supported by one singlepivotal track frame on opposite sides of the body. The frames are:provided with track wheels or belts. The'new suspension comprises ajournal bushing fixed to each of the pivotal frames and defining thepivot axis therefore. 1n the bushing are positioned thick-walled, solidtube-shaped elastic,

linings made of rubber or the like and which encompass a coaxiallyextending support beam mounted to the tractor body. The outside and theinside surfaces of the elastic linings are not rotatably joined to theinside of the bushing and the outside of the beam, respectively, suchthat the pivotal movements of the track frames when the tractor ismoving through terrain take place under flexible deformation of thelinings, which linings thus operate as spring suspensions and shockabsorbers.

1 Claim, 1 Drawing Figure Apr. 3, 1973 p PATENTEDAPRIi I975 m1 NS mamfl/vo ODD KPANE TH VE'DT I N V E N T ORS MW zwM ATTORNEYS pivotal bogiesprovided with track wheels.

SUSPENSION FOR PIVOTAL TRACK FRAMES ON TERRAIN MOTOR VEHICLES Thepresent invention relates generally to terrain motor vehicles, moreparticularly to a suspension for pivotal track frames on such vehicles.

The invention shall in the following be described in connection withbelt tractors, but it shall be understood that the invention is alsoapplicable to tractors with The present invention relates to pivotaltrack frames of the kind including spring means which partially supportthe tractor body, and partially suspend the track frames.

PRIOR ART US. Pat. No. 2,654,614 relates to a suspension whereby thefore part of the tractor body is provided with a laterally extendingleaf spring means, the outer end of which is in engagement with each ofthe pivotal track frames. The track frames are pivotally supported at adistance behind the leaf spring means.

From Swedish patent No. 126,044 is known a tractor design whereby thevehicle is provided with a single pivot frame for the track wheelsand/or the belts on opposite sides of the tractor body. Between thepivotal frames and the chassis or tractor body is provided torquesuspension means, the frames being coupled together such that a turningmovement of one of the tracks relative to the tractor body in onedirection results in a corresponding turning movement of the other trackframe in the opposite direction.

A drawback with known terrain motor vehicles of this kind is that it hasproved difficult to provide an ideal combination of good springsuspension, satisfactory terrain moving properties, avoidance ofvibrations and/or bumps and finally too much wear on the vehicle assuch. I

The principle object of the present invention is therefore to provide animproved terrain motor vehicle which thus possesses good stability inthe terrain, improved ability to drive in rough terrain, and whichfurthermore provides relatively good driving comfort with avoidance ofexcessive bumps and vibrations.

The suspension for pivotal track beams on terrain motor vehicles inaccordance with the invention is of the kind where the tractor body issupported by pivotal track frames on opposite sides of the body, whichframes are provided with track wheels or belts. The suspension comprisesa hollow bushing fixed to each of the pivotal frames and defining thepivot axis, the bushings extending transversely towards the tractorbody. In the bushings are positioned thick-walled, solid tube-shapedelastic linings made of rubber or the like, which encompass a likewisetransversely coaxially extending support beam mounted to the tractorbody. The outside and the inside surfaces of the elastic linings arenon-rotatably joined to the inside of the bushing without influencingthe position or state of the tractor body and/or the other pivotal trackframe, the latter thus maintaining full track position relative to theground.

The common pivot axis of the pivotal track frames is preferably arrangedat a predetermined distance behind the mid-point of each respectivetrack frame, that is behind the mid-point between the foremost and therearmost supporting point against the ground. The resulting outer ofgravity of the tractor, taking into account the chassis with engine,driver, load etc., is preferably arranged at a distance ahead of thepivot axis. The magnitude or size of the moments transferred from thetractor and which must be absorbed by the elastic linings will thus bethe total weight of the tractor multiplied by the minimum distance fromthe center of gravity thereof to the line or axis through the supportshaft. When the vehicle stands on horizontal ground, 50 percent of .thetorque load will be absorbed by each belt bogie, which .torque furtherresults in a cor responding torque in the belt, and which is balanced bya correspondingly large upwardly directed moment against the fore partof the belt.

When the belt during driving hits an obstruction and receives arelatively large proportion of the torque from the tractor body, and theother belt bogie receives correspondingly less torque, the tractor bodywill position itself in an intermediate position or level between theangular positions of each'of the belt bogies.

The invention will be better understood by the fol- I lowing descriptiontaken in connection with the accompanying drawing, wherein there isillustrated an embodiment of a suspension in accordance with theinvention, the single FIGURE showing a plan view, partly in section, ofa motor vehicle provided with a suspension in accordance with theinvention.

In the FIGURE the reference number 1 designates the tractor body orchassis, on the rear portion of which is positioned the engine 4. Thechassis has a fore part 6 including an area 8 for the driver. Thechassis l is rigidly connected, for instance welded or bolted, to thesupport beam 10 via a support hub 12. The support beam 10 is designatedas a hollow cylinder as shown. In

the FIGURE the right part of the support beam 10 with correspondingparts are shown in section for the sake of clarity, and since the rightpart and the left part of the vehicle are identical, it is onlynecessary to describe one of these parts.

Inside the hollow support beam 10 is, in the illus trated embodiment,joumalled a torsion rod 14 the inner end of which is rigidly connectedin a block 16 which is rigidly connected to the support beam 10. Theouter end of the torsion rod 14 is supported in a rubber packing 20,which is provided with a conical outside 22, which rests against acomplementary conically shaped end portion 24 of the support beam 10.The outer end 18 of the torsion rod is provided with an enlarged, notcircular, end portion or extension 26 which firstly serves to keep therubber packing 20 in place and secondly serves as a non-rotatablesupport for a lever arm 28, the outer end of which is fixed, forinstance by means of bolts, to a bracket 30 which constitutes a rigidpart of the pivot beam or frame 32 for the belt bogie.

On the pivot beam 32 is mounted a relatively long, transversallyextending, strong journal bushing 34 which rotatably encompasses thesupport beam 10. Between the bushing 34 and the beam is provided asubstantial clearance which is filled with a thick tubeshaped lining 36of rubber which thus serves as spring means and bumper means and is innon-rotatable engagement with the support beam as well as with thejournal bushing 34. All pivotal movements and torques transferred fromthe track frames are absorbed by rubber linings 36 which thus aresubjected to a constant, but varying elastic deformation during thedriving. Please note that the use of torsion rods 14 as shown as anadditional torque absorbing means is auxiliary and in most casessuperfluous.

The power transfer from the engine of the tractor chassis to each of thebelt drives constitutes no part of the'present invention and may besolved in several per se conventional fashions. In the motor vehicleshown in the drawing the power transfer from the motor on the tractorbody to each of the belt bogies take place via a V-belt system 40. Asshown in the FIGURE the torque from the motor 4 is transferred via theV-belt 40 to one on the bogie drive shaft 42 which over the chain drive44 transfers the power to the wheel 46 for the belt 48. (Removed on theright side of the tractor in the FIGURE).

The center of gravity for the entire tractor is designated with theletter T. The exact position of the center of gravity will naturallyvary in accordance with I the load which at any time is put on thetractor. The

weight P on the tractor will however generate a torque M P-a,

wherein a is the horizontal distance from the center of gravity to thevertical axis through the support beam. This moment or torque will inthe illustrated embodiment, via the support beam and the lever arm 28 betransferred to the rubber linings and the torsional rods 14,simultaneously as the belts through the belt bogies provide thenecessary, oppositely directed torque such that balance is obtained.

Each pivotal track frame will, via the belts or wheel bogies, absorbrespective parts of the prevailing torque and in the torque absorbingmeans will exist corresponding, oppositely directed torques. When thebelt bogies are parallel viewed from the side, the moments in each ofthe rubber linings and possible torsional rods will be equal. When thebogies are in an angular position relative to each other, the bogiewhich is directed more upwardly than the other will receive a relativelygreater proportion of the torque from the tractor body, and possiblyalso a part of the torque stemming from the other bogie, with theconsequence that the torque absorbing means of that part of the tractorwill receive a greater part, possibly the entire torque, from thetractor simultaneously as the tractor body turns the torque absorbingmeans further. This has the effect that the tractor body always willposition itself at a level or at an angle between the angular positionsof the respective belt bogies.

When building a tractor in accordance with the invention it has provedachievable to arrange the center of gravity of the tractor chassis orbody relatively far ahead of the pivot axis since thereby one obtains arelatively large pressure against the fore part of the track frames,whereby it occurs that the belts (or the front wheel in a wheel bogie)gets a good grip or track against the ground surface also when thevehicle is driven steeply uphill. It is furthermore possible to arrangethe pivot axis a good distance behind the midpoint of each track frame.

One may provide special bumpers or shock absorbers between the supportbeam and each respective track frame, but such means has not provednecessary, among other reasons because of the special power transferarrangement as shown, whereby the engine power is transferred viaV-belts to a drive shaft on each of the belt bogies, which drive shaftis not exactly concentric with the pivot axis of the belt bogies.

In order to limit the pivotal movements of each bogie one may on thesupport beam 10 attach stop members 53, or alternatively an extendedcylindrical part 29 of the support beam 10 provided with a torque leverarm 28, extended through an opening in the beam, such that the opposingend walls in the opening form abutments providing limitations for thepivotal movements of the lever arm 28 and thereby the pivotal movementsof each of the track frames.

A motor terrain vehicle inaccordance with the invention will possessexcellent terrain moving qualities, among other reasons because the beltbogie can undergo very large pivotal movements relative to each other,such that for instance one of the bogies may pass over a very large bumpin the terrain, for instance a large stone, without influencing thestability of the vehicle. This is possible because the tractor chassisor body itself will not follow upward and take part in the upwardlypivoting movement of the belt, and furthermore because the other belt toa large degree will remain in full track engagement with the groundsurface.

It is furthermore most feasable to utilize relatively large elasticlinings as torque absorbing means. In addition to elastic linings,usually made of rubber, one may also utilize torsion rods but trialshave shown that additional torsional rods are not necessary if the totalweight of the vehicle does not exceed 3-4 tons. The use of torsion rodsimplies that the flexible movements of the pivotal beams and thus thespring action will be more rigid or stiff having for instance the effectthat when one belt bogie hits a large unevenness and thus is pressedupwardly from the ground, the other belt bogie will also have a tendencyto move upwardly. This is not desirable since thereby the stability ofthe vehicle will be hampered and the track effect will be reduced.

Utilization of relatively elongated journal bushings 34 including theelastic linings for supporting the track frames have proved to involve avery satisfactory solution, since the design provides a very simple andrugged construction with relatively small bending stresses in thesupport system, among other reasons because the length of the journalbushings reduces bending stresses. The rubber linings operate also asbumpers both versus shocks straight against the belts and againstlateral bump and impacts against the bogies. As well known the bogies onbelt tractors are subjected to severe stresses and strains duringdriving in rough terrain. The belt bogies will thus be subjected tolateral forces, for instance during turning movements which usually take6 place by driving the one belt at a larger speed than the dinalmidpoint thereof; other, with the effect that the belts skid on theground. e. a pair of resilient linings, each having inner and Practicaltrial has shown that the rubber linings not outer surfaces, one of saidlinings being positioned only operate very effectively as torque andspring within each of said journals and surrounding said means, but alsooperate as effective bumpers against 5 pp beam, Said inner surfaces ofSaid linings shock and impact loads. being non-rotatably joined withsaid support beam, What is claimed isg and said outer surfaces of saidlinings being nonl.Aterrain vehicle o i i rotatably joined with saidjournals, said linings a. a vehicle body havin a enter f it therebybeing torsionally stressed by said vehicle b. a pair of pivotal trackframes positioned on op- 10 q ym posite sides of said vehicle body andextending lon- Sald PP beam, 5 ald l g and Said JQf gitudinallysubstantially the length thereof; concemncany j a P axis Rosltlofled c.a support beam extending transversely of said rearwardly f salfi f f off y of Sam vehicle vehicle body and rigidly attached thereto reap bodyand said midpoints of said track frames, said -dl f Said center fgravity; track frames thereby being independently, d. a pair ofjournals, one of said journals extending reslhently; P mounted formovement transversely of each of said track frames and around pwotaxlsrigidly attached thereto rearwardly of the longitu-

